CurtPalme.com Home Theater Forum

[opv]

Hi,
My PJ is a relatively new BG1209s with scheimpflug adjustments, HFQ-900 lenses.
I added shavers between the lenses and the tubes for more scheimpflug range.
I managed to get perfect uniform focus on the green tube.
I'm having some problems with getting perfect scheimpflug on the red tube.
For some reason, it's much simpler to find the correct optical focus on green than it is on red.
In the green tube I can tell from a distance if the focus is good, while in the red, the focus looks good but when I go closer to the screen I see it's not perfect.

I guess, that the red scheimpflug is also more complicated because it also depends on the correct projection angle.

My main questions are:
1) Any recommended test pattern for scheimpflug adjustment? the geometry patterns don't tell me much on the red tube, and the 1on 1 off patterns require that I stand very close to the screen.
2) Any tips you may have regarding this matter. the barco scheimpflug adjustments are diagonal ones and not horizontal vertical. I haven't found a procedure for adjusting such mechanism.

Thanks

[fuchs]

I've had some luck with a "self-photoshopped" set of dots and binoculars.
The dots are relatively easy to notice when they go out of focus.
Or maybe a couple of very fine lines close together in all 4 corners and the centre.
I'd try something with a pattern with very small in-between spaces so they will 'blend' noticably when out of focus.

If you can't get it super-sharp in whatever situation, you might want to double-check your electronic focus.

[opv]

fuchs,
Thanks for the tips.My electronic focus is just fine, I checked that by looking into the lens.
In the dot pattern you mentioned, what dot size would you recommend? 1 pixel (which is very hard to notice from distance) or bigger?

And one more question, I tried to use binoculars once for optical focus. It was a very disappointing experience for me. every time I changed the focus on the lens, and looked through the binoculars, I had to adjust the binoculars focus as well.

[fuchs]

well this may sound weird, but you could try larger dots (like 2px wide and 2px high, ... or 4x4 .... or whatever works) , at a low resolution (like 640x480) from a PC. Or from an un-upscaled DVD.

In that case the scanlines become visible.
If you notice the gaps between the individual scanlines inside the dots, your optical focus would be close to perfect.

The alternative that I can suggest, is the use of a videocamera. I used this approach actually.
I have an old Handicam camcorder on a tripod, zoomed in all the way on the part of the screen you're working on. The video-signal is fed to an old 12" CRT color video monitor that I put close by myself, on top of a cupboard or something.
I found this better than the binoculars, as you dont have to hold anything in your hand during adjustments.
Secondly, you don't have to look at the projection-screen while adjusting, the video-monitor can (ofcourse) be placed anywhere.
Finally, my eyesight is limited, even with binoculars I had to squint a lot and my eyes get tired soon.

I agree that red and blue (even when not de-focussed) are harder to get right, because of the projection angle.
Besides the fact that they are lower in intensity.